Launching and lowering gear for ships&#39; lifeboats



W. G. MOORE April 5, 1955 Filed m. 20

4 Sheets-Sheet l Inventor 01E,

Attorney Wa/zer 5/7 y W. G. MOORE April 5, 1955 4 Sheets-Sheet 2 Filed Feb. 20, 1951 M W 1 I M m a w G 9 Hm a W n n u n n u Q\//. J i J. .w Q 4w n w 2 z -Ll l l 1 -:m 1: i2 -l ..h

W. G. MOORE LAUNCHINC AND LOWERING GEAR FOR SHIPS LIFEBOATS F' iled Feb. 20. 1951 4 Sheets-Sheet 3 Attornfy April 5, 1955 w. G. MOORE 2,705,332

LAUNCHING AND LOWERING GEAR FOR SHIPS LIFEBOATS Filed Feb. 20, 1951 4 Sheets-Sheet 4 lrzvnlor Wei/fer G. Mao/"e AlIonzey United States Patent LAUNCHING AND LOWERING GEAR FOR SHIPS LIFEBOATS Walter G. Moore, Liverpool, England, assiguor to Marepa Trust Limited, Tankerton, England, a British company Application February 20, 1951, Serial No. 211,908 Claims priority, application Great Britain August 15, 1950 Claims. (Cl. 9-68) This invention is for improvements in or relating to gravity davits of the kind in which the davit arm is pivoted on a swinging linkage and moves, during its outboard movement, about two or more pivots so that the davit arm has a substantial outreach without requiring a large amount of headroom when in the stowed position.

According to one feature of the present invention there is provided a gravity davit comprising a stand, a davit arm, and a linkage having a pivotal connection to the stand and a pivotal connection to the arm so that the arm is floatingly suspended from the stand by said link, a guiding member acting on the arm so as to constrain it to following a predetermined path during its outboard movement on said link, and means for limiting movement of the arm at its fully extended position.

In davits of the kind with which the present invention is concerned the arm moves, in effect, not about one pivot only but about two or more pivots. In davits of this kind as constructed heretofore the direction of movement of the davit head has generally been subjected to a sudden change as the movement of the arm changes from one pivot or fulcrum to the next. This is objectionable as what is required is a smooth action without abrupt changes in the direction of movement of the davit head. Such abrupt changes have an adverse effect on the operating winch. The davit according to the present invention has a smooth movement right from the inboard to the fully outboard position. Furthermore the arrangement is such that not only does the arm swing forwardly but its pivots also swing forwardly so that a substantial outreach is obtained whilst at the same time ensuring gravity action even though the ship on which the davit is mounted may have a serious adverse list.

According to a further feature of the present invention there is provided a gravity davit comprising a stand, a

davit arm having a rearward part towards its lower end,

a rear link having one of its ends anchored to the davit stand and its other end anchored to said rearward part, and a front link anchored to the stand and to the lower end of the davit arm.

This arrangement provides a fully floating suspension for the davit arm which permits an unobstructed and smooth outboard swinging action in which the fulcrum about which the arm swings follows the load on the arm in such a manner as to avoid any abrupt changes or peak loads. Furthermore, by employing a guiding member in the form of a link instead of a runway or guiding surface, efliciency of operation is promoted. Guiding surfaces as used heretofore often become fouled by neglect or painting and obstruct free movement of the arm. With an arrangement according to the present invention the arm is subjected to a minimum of frictional resistance to its movement. Further the absence of runways or similar guiding surfaces serves to promote a silent and smooth action of the davit.

The terms front and rear where used in this specification in relation to the links supporting the davit arm, are synonymous to the terms outboard and inboard.

According to a further feature of the present invention there is provided a gravity davit comprising a stand, a davit arm having a rearwardly projecting part towards its lower end, a rear link having a pivotal anchorage on the stand and depending from said anchorage and having its free end pivotally connected to said rearwardly projecting part, and a front link having a pivotal connection ill) to the stand and a pivotal connection to the lower end of the davit arm.

According to a still further feature of the present invention there is provided a gravity davit comprising a stand, a davit arm having a rearwardly projecting part towards its lower end, a substantially vertical rear link having its upper end pivotally connected to the stand and its lower end pivotally connected to said rearwardly projecting part at a point thereon remote from the arm, and a substantially horizontal front link having its forward end pivotally connected to the stand and extending inboard and having its other end pivotally connected to the toe of the davit arm. The positions of the links just referred to are those they occupy when. the davit is in the inboard or stowed position.

The rear link may act as a tie to limit outboard movement of the arm at the fully outboard position. Similarly, inboard movement of the arm may be limited by the front link acting as a tie. Additional stops may be provided for limiting movement of the arm.

From another point of view, the present invention provides a gravity davit wherein the davit arm has a continuous luifing action about a position or positions created by two suspension members anchored to the davit stand one of said members being connected to the heel of the davit arm and other being connected to the toe thereof. The result of this novel mode of suspension is that the davit arm moves bodily forward in a manner which causes its head to follow a straight, or substantially straight, path for at least the greater portion of its outboard movement from the stowed position. Of said two suspension members, conveniently, one is brought into tension by the outboard movement of the arm and serves to limit said outboard movement at the fully outboard position and the other may be brought into tension or otherwise caused to act, by the inboard movement of the arm, so as to serve to bring the arm to rest at the fully inboard position.

Some specific embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings. On the drawings:

igure 1 is a side elevation of a boat launching gear including davits in accordance with the invention, the davit arm being in its inboard or stowed position,

Figure 2 is a front elevation of the launching gear shown in Figure 1,

Figure 3 is a further side elevation of the launching gear but with the davit arm in its partly extended posit1on,

Figure 4 is a still further side elevation showing the dagit arm in its fully extended, or outboard position, an

Figure 5 is a cross-section on the line VV of Figure 4 and shows, more particularly, a stop arrangement for limiting outboard movement of the arm.

For a ships lifeboat there are, of course, two davits by and between which the boat is supported.

Each davit comprises a stand 10 mounted, for example, on the ships deck or on the roof of a deck house, or as in the case shown in Figures 1 to 4 of the drawing, partly on the deck 11 and partly on the deck house 12, the leg 10a of the stand being adjacent the ships rail. The davit also comprises a davit arm 13 of the conventional curved form except that a bracket 14 is formed on or secured to a rear face or heel portion 15 at the lower end of the arm. The bracket 14, in the case shown, extends rearwardly or inboard of the arm and is of triangular shape the base of the triangle being formed by the heel portion 15, of the arm. A link 16 is pivotally connected to and depends from an anchorage 17 at the rear upper portion of the stand 10. A further and shorter link 18 is pivotally anchored at 19 to a lower and forward part of the stand. The link 16, at its free end, is pivotally connected at 20, whilst the other link 18 has its free end pivotally connected to the toe at the lower foremost extremity of the arm as indicated at 21. The arm 13 carries the usual keel supporting block 22 which helps to support and position the boat B when the latter is in the stowed position. It will be noted that the davit arm has the usual sheaves 23, for the launching tackle 24, and a horn 13a from which the boat is suspended in the usual way when it is in the stowed position. The tackle 24 may be connected to and operated by the usual form'of winch.

In the inboard or stowed position of the davit arm and boat the rear link 16 hangs downwardly substantially vertically and the front link 18 extends inwardly (i. e. inboard) approximately horizontally. During outboard movement of the arm (i. e. during a boat launching operation) the link 16 swings forwardly and upwardly whilst the link 18 swings forwardly and downwardly. Thus, there is a downward and outboard swinging movement of the pivot 21 and it is about this pivot, in effect, that the davit arm pivots outboard. The result is that the head of the davit arm moves outboard in a substantially straight path, at least during the first portion of its outboard movement, and the boat is taken smoothly and steadily out over the ships side. The path of movement of the davit arm head is indicated by chain lines in Figure 3.

It will be noted that whilst the arm operates to some extent about a double or multiple pivot arrangement, there is no objectionable sudden change or dip in the path of the movement of the davit arm head as happens in many cases of multiple pivot davits as constructed heretofore.

The inclined member 100 of the stand at least is preferably made of angle section members having their lateral flanges turned inwardly. The links or suspension members 16 and 18 and the arm 13 are arranged to work between these members of the stand so that the latter gives lateral support to the suspension members or links and to the arm.

Movement of the arm at the fully outboard position is halted by lateral projections 25 (see Figures 4 and 5) on the link 16 coming up against the inturned flanges on the inclined part 100 of the stand. Inboard movement of the arm 13 is halted by said arm coming up against the stop afiorded by the pivot 17 for the link 16.

In Figures 1 to 5 it, will be noted that at the fully outboard position of the arm 13 the link 16 is in tension whereas during inboard'movernent of the arm the link 18 is brought into tension.

I claim:

1. In a gravity davit a stand, a davit arm" having a permanent outboard bias and having a forwardly located toe part and a rearwardly located heel part at its lower end, a rear link, pivot means at one end of said rear link pivotally suspending it from a rearward part of the stand, pivot means at the other end of'said rear link pivotally connecting it to said heel of the davit arm, a front link substantially shorter than the rear link, pivot means at one end of said front link pivotally suspending it from the stand, pivot means at the other end of said front link pivotally connecting it to the toe part of the davit arm, to the rear of its pivotal connection to the stand, and stop means for halting outboard movement of the davit arm before the rear link to davit arm pivot passes through a straight line joining the link-to-stand pivots.

2. In a gravity davit a stand, a davit arm having a permanent outboard bias and having a forwardly located toe part and a rearwardly located heel part at its lower end, a rear link, pivot means at one end of said rear link pivotally suspending it from a rearward part of the stand, pivot means at the other end of said rear link pivotally connecting it to said heel of the davit arm, a front link substantially shorter than the rear link, pivot means at one end of said front link pivotally suspending it from the stand, pivot means at the other end of said front link pivotally connecting it to the toe part of the davit arm, to the rear of its pivotal connection to the stand, and cooperating stop means on the rear link and the stand for halting outboard movement of the davit arm before the rear link to davit arm pivot passes through a straight line joining the link-to-stand pivots.

3. In a gravity davit a stand, a davit arm having a permanent outboard bias and having a forwardly located toe part and a rearwardly located'heel part 'at its lower end, a rear link, pivot means at one end of said rear link pivotally suspending it from a rearward part of the stand, pivot means at the other end of said rear link pivotally connecting it to said heel of the davit arm, a front link having a length not greater than half that of the rear link, pivot means at one end of said front link pivotally suspending it from the stand, pivot means at the other end of said front link pivotally connecting it to the toe part of the davit arm, to the rear of its pivotal connection to the stand, and stop means for halting outboard movement of the davit arm before the rear link to davit arm pivot passes through a straight line joining the link-to-stand pivots.

4. In a gravity davit a stand, a davit arm having a permanent outboard bias and having a forwardly located toe part and a rearwardly located heel part at its lower end, a rear link, pivot means at one end of said rear link pivotally suspending it from a rearward part of the stand, pivot means at the other end of said rear link pivotally connecting it to said heel of the davit arm, a front link substantially shorter than the rear link, pivot means at one end of said front link pivotally suspending it from the stand, pivot means at the other end of said front link pivotally connecting it to the toe part of the davit arm, to the rear of its pivotal connection to the stand, and stop means for halting outboard movement of the davit arm before the rear link to davit arm pivot passes through a straight line joining the link-to-stand pivots, the distance between the two pivots on the arm plus the length of the rear link being substantially greater than the distance between the two pivots on the stand.

5. In a gravity davit a stand, a davit arm having a permanent outboard bias and having a forwardly located toe part and a rearwardly located heel part at its lower end, a rear link, pivot means at one end of said rear link pivotally suspending it from a rearward part of the stand, pivot means at the other end of said rear link pivotally connecting it to said heel of the davit arm, a front link substantially shorter than the rear link, pivot means at one endof said front link pivotally suspending it from the stand and pivot means at the other end of said front 'link pivotally connecting it to the toe part of the davit arm, to the rear of its pivotal connection to the stand and stop means for halting outboard movement of the davit arm before the rear link to davit arm pivot passes through a straight line joining the link-to-stand pivots, whereby the davit arm is supported pendulum-fashion from the stand at all times, the angular movement of the links being approximately equal to the angular movement of the arm during operation of the davit.

References Cited in the file of this patent Rogers, John Wiley & Sons, Inc., 1931; page 354. 

